The present invention relates to antennas, and, more particularly, to an antenna for a vehicle in an Intelligent Transportation System.
In an Intelligent Transportation System (ITS), vehicles are expected to be able to connect to everything (e.g., vehicle-to-everything (V2X)), which means that a vehicle should be able to connect to other vehicles, as well as with other road users and infrastructures. For example, modern vehicles are expected to be able to receive such signals as AM/FM radio signals, Global Positioning System (GPS) signals, wireless communication signals, such as 3G, 4G and LTE signals, and Wi-Fi. Modern vehicles also will be expected to communicate with other ITS infrastructures using Dedicated Short Range Communications (DSRC) for road safety and traffic efficiency. All these signals are transmitted at different frequencies, requiring various antennas for receiving these signals. However, having multiple antennas mounted all over the vehicle is costly and unsightly, so antennas that integrate multiple antennas into a shark-fin shaped housing have become popular.
A typical vehicle shark-fin unit has a length of 100 mm, width of 45 mm and height of 50/55 mm. This small size brings many challenges to the antenna design. For example, the smaller the distance is between antennas, the stronger the mutual coupling effects, and the lower the height of the unit, the more difficult it is to achieve low frequency applications. The limited space also makes it difficult to achieve a sufficient return loss and an omnidirectional radiation pattern. Thus, there has been many studies on antenna development for vehicular communications. However, none of the proposed designs with the desired footprint is able to cover all of the desired frequency bands, and provide adequate performance in both return loss and radiation patterns, and avoid mutual coupling among the multiple bands or antenna ports.